Ho-155 cannon

"Ho-155" redirects here. For the isotope of holmium (Ho-155 or ¹⁵⁵Ho), see Holmium-155.

The 30 mm Ho-155 cannon was a Japanese aircraft autocannon used during World War II, often mistakenly called with the Ho-105 or Ho-151. A lighter and more compact Ho-155-II was designed towards the end of the war.^[2]

Ho-155 cannon
Type	Aircraft cannon
Place of origin	Imperial Japanese army
Service history
Wars	World War II
Specifications
Mass	Ho-155-I: 50 kg (110 lb 4 oz) Ho-155-II: 44 kg (97 lb 0 oz)
Length	Ho-155-I: 1,750 mm (69 in) Ho-155-II: 1,510 mm (59 in)
Barrel length	Ho-155-I: 1,140 mm (45 in) Ho-155-II: 980 mm (39 in)
Cartridge	30 x 114mm (235 g)
Calibre	30 mm (1.2 in)[1]
Action	Short recoil-operated
Rate of fire	450-500 rounds/min
Muzzle velocity	715 m/s (2,350 ft/s)
Effective firing range	900 m
Feed system	Belt

Development

Had the war continued longer the Ho-155-II would most likely have seen service on the jet-powered Karyu Ki-201

The Ho-155-I was first began development in 1942 as a scaled-up and modified version of the 20mm Ho-5 cannon,^[1] itself a scaled-up Model 1921 aircraft .50-inch Browning machine gun. In 1943-44 began development of the Ho-155-I and in late 1944 began the development and production of the Ho-155-II^[1] for fit into tighter wing bays of fighter planes such as the Ki-84-Ic,^[1] Ki-102 and on the project design of the jet-powered Ki-201.^[3]

Unknown service

Simultaneously the Ho-155-I and Ho-155-II were produced in Nagoya by the Nagoya Army Arsenal, but as the war was prolonged leading to shortages of materials it is not known how many were eventually produced or how many actually saw service. However it became an example of ingenuity and design from the simple basic design of the Browning machine gun.